Elliot Formation

Elliot Formation
Stratigraphic range: Norian-Pliensbachian ~
File:Elliot Formation Caves in 'Matalane Valley, Leribe, Lesotho - panoramio.jpg Elliot Formation caves in the Matalane Valley, Leribe, Lesotho
Type	Geological formation
Unit of	Stormberg Group
Sub-units	Upper Elliot, Lower Elliot
Underlies	Clarens Formation
Overlies	Molteno Formation
Thickness	up to 500 m (1,600 ft)
Lithology
Primary	Mudstone, sandstone
Other	Siltstone, conglomerate
Location
Coordinates
Approximate paleocoordinates
Region	Eastern Cape, Free State, Mafeteng, Maseru, Quthing, Qacha's Nek & Mohale's Hoek
Country	Lesotho South Africa
Type section
Named for	Elliot, Eastern Cape
Elliot Formation is located in South Africa Elliot Formation Elliot Formation (South Africa)

The Elliot Formation is a geological formation and forms part of the Stormberg Group, the uppermost geological group that comprises the greater Karoo Supergroup. Outcrops of the Elliot Formation have been found in the northern Eastern Cape, southern Free State, and in the eastern KwaZulu-Natal provinces of South Africa. Outcrops and exposures are also found in several localities in Lesotho such as Qacha's Neck, Hill Top, Quthing, and near the capital, Maseru. The Elliot Formation is further divided into the lower (LEF) and upper (UEF) Elliot formations to differentiate significant sedimentological differences between these layers. The LEF is dominantly Late Triassic (Norian-Rhaetian) in age while the UEF is mainly Early Jurassic (Hettangian-early Pliensbachian) and is tentatively regarded to preserve a continental record of the Triassic-Jurassic boundary in southern Africa. This geological formation is named after the town of Elliot in the Eastern Cape, and its stratotype locality is located on the Barkly Pass, 9 km north of the town.

Geology

The Elliot Formation unconformably overlies the Molteno Formation and is conformably overlain by the Clarens Formation. Due to the reddish colour of the rocks, the Elliot Formation is colloquially referred to as the "Red Beds" in older geologic literature.

The Elliot Formation is dominated by mudstones and siltstones that can be finely laminated. However, the internal structures in the mudstones are often not visible due to locally poor laminations. Calcareous nodules are also found in the mudstone layers and become more frequent up section into the UEF. The mudstones range in colour from greyish purple red in the LEF and turn a more brick red colour with more mature palaeosols in the UEF. Localized intraformational pebble conglomerates that comprise intrabasinal clasts that comprise mud chips, quartzite pebbles, pedogenic nodules, and fossil bone fragments only occur in the UEF. The lower and upper Elliot formations both contain sandstones but they vary in their internal geometries. The sandstones of the LEF mainly comprise laterally accreting channel deposits that are multi-story and contain trough, low angle, and planar, cross-bedding. Ripple cross laminations with good horizontal lamination are also present. In the UEF, sandstone beds are single story and mainly reflect downstream accretion channel geometries and are more tabular in appearance. Common internal sedimentary structures of UEF sandstones are planar, low angle cross-bedding, horizontal and ripple-cross laminations.

The LEF was deposited in a fluvio-lacustrine environment where rivers were more perennial and formed meandering channel geometries, as evidenced by the presence of lateral accretion. However, this depositional environment changed at the onset of the UEF deposits where evidence of shallower river channels, longer periods of floodplain stasis (mature palaeosols) and flash flood events (pedogenic nodule conglomerates) shows that the climate became more arid.

Correlation

The Elliot Formation is currently considered to correlate chronostratigraphically with geological formations of the Bodibeng Sandstone of the Tuli Basin in Botswana, the Omingonde Formation of the Etjo Basin in Namibia, and the Chinle Formation of the Colorado Plateau in Utah, United States.

Age

U-Pb radiometric dating using zircon grains has refined the duration of the Elliot Formation. Zircons of the Lower Elliot Formation are entirely Late Triassic, ranging from around 220 to 205 million years old (Norian to Rhaetian stages). Zircons of the Upper Elliot are mostly Early Jurassic, ranging from around 202 to 192 million years old (latest Rhaetian to Sinemurian stages). The oldest zircons of the overlying Clarens Formation are about 187 million years old (mid-Pliensbachian stage).

The entire Elliot Formation also preserves a record of magnetostratigraphy, with at least nine reverse-normal polarity chron pairs (EF1r to EF9n). The lower-upper Elliot boundary is in the middle of chron EF6n. The Elliot Formation's magnetostratigraphy can be partially correlated with similar records in the Newark Basin (northeast United States), Chinle and Moenave formations (southwest United States), and Los Colorados Formation (Argentina).

Paleontology

The Elliot Formation is well known for its diverse dinosaur fossils. The most common dinosaur species is of the sauropodomorph species Massospondylus carinatus. Other species include Blikanasaurus cromptoni, Aardonyx celestae, Euskelosaurus browni, Antetonitrus ingenipes, Pulanesaura eocollum, and the largest sauropodomorph yet found, Ledumahadi mafube. Fossilised Massospondylus eggs, some with the fossilized remains of embryos intact, have been recovered from UEF deposits in the Golden Gate Highlands National Park. Euskelosaurus fossils are more common in the LEF while Massospondylus are only found in the UEF. The basal ornithischian dinosaurs, Heterodontosaurus tucki, Lesothosaurus diagnosticus, Abrictosaurus consors, and Lycorhinus angustidens have also been recovered from the UEF. In addition this formation has yielded various crocodylomorph species, namely Litargosuchus leptorhynchus, Sphenosuchus acutus and Orthosuchus stormbergi. A large theropod dinosaur, Dracovenator regenti, has been found in the UEF. Synapsids from the formation include the dicynodont Pentasaurus goggai the tritheledontid cynodont Elliotherium kersteni and the mammaliaform Megazostrodon rudnerae. More recent vertebrate fossil finds near the town Qhemegha in the Eastern Cape have yielded possible fossil material of a poposauroid pseudosuchian. The rhaptochelydian turtle Australochelys is known from the upper parts of the formation. A giant brachyopoid temnospondyl from the formation is considered to be one of the largest known amphibians. The mudstones of the LEF sometimes yield petrified wood, fossil plant matter, crustaceans, fishes, and turtles while the sandstones of the upper Elliot Formation more often contain various trace fossils. These include vertebrate trackways of basal ornithischian dinosaurs found in the Leribe, Mafeteng, and Mohales Hoek Districts of Lesotho. Possible trackways of the dicynodont Pentasaurus have been found on Morobong Hill in the Mohales Hoek District of Lesotho. Trackways from a large theropod referred to the ichnotaxon, Kayentapus ambrokholohali have been found, measuring 57 centimetres (22 in) in length.

Dinosaurs

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Ornithischians

Ornithischians of the Elliot Formation
Genus	Species	Location	Stratigraphy	Notes	Images
Abrictosaurus	A. consors		Upper Elliot	A heterodontosaurid, formerly species of Lycorhinus	File:Abrictosaurus dinosaur.png
Eocursor	E. parvus		Upper Elliot	A basal ornithischian	File:Eocursor BW.jpg
Fabrosaurus	F. australis		Upper Elliot	A basal ornithischian, nomen dubium
Heterodontosaurus	H. tucki		Upper Elliot	A heterodontosaurid	File:Heterodontosaurus restoration.jpg
Lesothosaurus	L. diagnosticus		Upper Elliot	A basal neornithischian or thyreophoran, formerly considered a species of Fabrosaurus	File:Lesothosaurus diagnosticus.png
Lycorhinus	L. angustidens		Upper Elliot	A heterodontosaurid
Pegomastax	P. africana		Upper Elliot	A heterodontosaurid	File:Pegomastax africana reconstruction.jpg
Thyreophora	Thyreophora indet		Upper Elliot	Known from scutes

Sauropodomorphs

Prosauropods of the Elliot Formation
Genus	Species	Location	Stratigraphy	Notes	Images
Aardonyx	A. celestae		Upper Elliot	A derived sauropodomorph	File:Aardonyx NT.jpg
Antetonitrus	A. ingenipes		Upper Elliot	A derived sauropodomorph or basal sauropod	File:Antetonitrus reconstruction.jpg
Arcusaurus	A. pereirabdalorum	Spion Kop Heelbo	Upper Elliot	A basal sauropodomorph, known from juveniles	File:Arcusaurus LM.png
Blikanasaurus	B. cromptoni	Blikana Mountain	Lower Elliot	A derived sauropodomorph or basal sauropod
Eucnemesaurus	E. fortis		Lower Elliot	A possible riojasaurid
	E. entaxonis
Euskelosaurus	E. browni		Lower Elliot	A plateosaurid, potentially dubious
Gryponyx	G. africanus		Upper Elliot	A massospondylid, potentially dubious
Ignavusaurus	I. rachelis		Upper Elliot	A massospondylid, known from a juvenile, potential synonym of Massospondylus
Kholumolumo	K. ellenbergerorum		Lower Elliot	A basal sauropodiform
Ledumahadi	L. mafube			A derived sauropodomorph or basal sauropod, largest in the formation	File:Ledumahadi NT.jpg
Massospondylus	M. carinatus		Upper Elliot	A massospondylid, most common fossil found	File:Massospondylus reconstruction.png
	M. kaalae		Upper Elliot	A massospondylid, differs from M. carinatus in cranial features
Melanorosaurus	M. readi	Thaba 'Nyama	Lower Elliot	A derived sauropodomorph	File:Melanorosaurus life restoration 2018.jpg
Meroktenos	M. thabanensis	Thabana Morena	Lower Elliot	A derived sauropodomorph, formerly a species of Melanorosaurus	File:Right femur of Meroktenos.png
Plateosauravus	P. cullingworthi		Lower Elliot	A basal sauropodomorph, formerly specimens of Euskelosaurus
Pulanesaura	P. eocollum		Upper Elliot	A derived sauropodomorph or basal sauropod	File:Pulanesaura eocollum.jpg
Sefapanosaurus	S. zastronensis		Upper or Lower Elliot	A derived sauropodomorph

Theropods

Theropods of the Elliot Formation
Genus	Species	Location	Stratigraphy	Notes	Images
Dracovenator	D. regenti	Upper Drumbo Farm	Upper Elliot	A dilophosaurid	File:Dracovenator regenti.jpg
Megapnosaurus	M. rhodesiensis	Syntarsus site.	Upper Elliot	A coelophysid	File:Coelophysis rhodesiensis.JPG

Pseudosuchians

Pseudosuchians of the Elliot Formation
Genus	Species	Location	Stratigraphy	Notes	Images
Basutodon	B. ferox		Lower Elliot	A dubious suchian
Litargosuchus	L. leptorhynchus	Eagles Crag Farm	Upper Elliot	A basal crocodylomorph	File:Litargosuchus leptorhynchus.jpg
Orthosuchus	O. stormbergi		Upper Elliot	A possible protosuchid
Rauisuchian			Lower Elliot	A indeterminate large "Rauisuchian"
Sphenosuchus	S. acutus		Upper Elliot	A large basal crocodylomorph

Synapsids

Synapsids of the Elliot Formation
Genus	Species	Location	Stratigraphy	Notes	Images
Elliotherium	E. kersteni		Lower Elliot	A tritheledontid cynodont
Megazostrodon	M. rudnerae		Upper Elliot	A megazostrodontid cynodont	File:Megazostrodon sp. Natural History Museum - London.jpg
Pentasaurus	P. goggai		Lower Elliot	A stahleckeriid dicynodont
Scalenodontoides	S. macrodontes		Lower Elliot	A very large traversodontid cynodont